What is chain isomerism?

Chain isomerism refers to the phenomenon where compounds have the same molecular formula but differ in the arrangement of their carbon skeletons. This type of isomerism occurs when the carbon chain can be organized in different ways, leading to variations in the structure without changing the overall composition of atoms.

For instance, consider butane (C4H10), which has two chain isomers: n-butane (a straight-chain structure) and isobutane (a branched structure). These variations in the arrangement of the carbon atoms are what define chain isomerism.

The other choices do not accurately describe chain isomerism; they focus on different aspects of isomerism, such as functional group placement, variations in atom composition, or the hybridization state of carbon atoms, which are not relevant to the concept of chain isomerism. Thus, the correct definition of chain isomerism is based on varying chain lengths and structures formed from the same molecular formula.